Studying the health effects of underground coal dust

The return of black lung

Dr Thure Edward Cerling, professor of biology, geology and geophysics at the University of Utah and chair of the study committee, says: “There is a clear increase in the incidence of black lung disease in underground coal miners over the past nearly 20 years, after a significant decrease from 1970 to 2000.”

Deaths related to black lung declined between 1970 and 2000, but the disease has since resurged and is progressing rapidly in certain regions of central Appalachia in the eastern US. Grievous symptoms of black lung have been known to appear in a five-year period, sometimes even less.

The US Mine Safety and Health Administration (MSHA) reduced the maximum allowable levels of dust in mines under the 2014 Respirable Coal Dust Rule.

Under the law, the MSHA “sets forth a respirable dust standard that limits miners’ exposures to airborne respirable coal mine dust (RCMD) in underground coal mines to 1.5 mg/m³ during the full shift that the miner works,” as written in the study.

In addition, the MSHA urges coal miners to wear a continuous personal monitoring device (CPDM). This can “continuously monitor RCMD concentrations and provide measurements of exposure concentrations in near real time to the miners wearing the device. CPDM readings provide wearers the opportunity to take steps deemed appropriate to reduce their exposures, where possible”.

There are still some serious challenges to implementation, not least ensuring miners use the device correctly. Employees are not tested in their proficiency in using the device, although it is considered simple to utilise.

The study continues: "No amount of training can resolve this paradox inherent in the current use of the CPDM… The mine operator may require the miner to move, as it could be viewed as unethical to require a miner to stay in a high-exposure location, as indicated by the CPDM, when a safer location is available. However, when the CPDM is used for compliance monitoring, changing a miner’s location renders the sampling unrepresentative of the highest exposures.”

While there are currently no treatments to successfully reverse black lung disease, increasing mine worker “participation in the voluntary medical surveillance system for early disease detection is significant”, the report claims, noting the lack of worker participation in assessment programmes.

It advises that mine operators should link data relating to employment and health histories of active and retired miners to medical surveillance programmes. This data would include duration of work at the coal face and use of gas masks over that period.

The study also explores approaches to dust sampling and ways to limit miners’ exposure to dust. Controlling dust exposure, especially crystalline silica, is critical to preventing black lung disease. Monitoring standards must go above and beyond the current federal regulations to save more coal miners from deadly inhalation.

“There are several reasons that could contribute to this increase in black lung and addressing the problem will require cooperation between government and industry in implementing new ways to address coal mine dust in the workplace, including advances in methods for monitoring dust concentrations in the workplace,” Cerling says.

“Due to the latency in the disease, it is likely to be some time before we know if any measures achieve success.”

The committee said that organisations such as the MSHA, the National Institute for Occupational Safety and Health (NIOSH) and the National Mining Association (NMA) are carrying out their own full investigations to identify the challenges of implementing a ‘beyond-compliance’ approach to dust monitoring in US mines.

While the MSHA and NIOSH are still reviewing the report, a spokesperson for the NMA, Conor Bernstein, says the NMA are “in absolute agreement that more must be done to significantly enhance health protection for our nation’s coal miners”.

He notes that while a ‘beyond-compliance’ approach may be a new term for the National Academy of Sciences, mine operators have been pursuing this strategy for decades.

“MSHA’s work might culminate in the collection and processing of dust samples for compliance purposes, but company work goes much deeper than that. Companies have to plan and design the entire mining environment, including dust control measures and ventilation, equipment maintenance and inspection, and employee training,” says Bernstein.

While the MSHA and the NIOSH suggest that lowering the respirable dust standard will reduce or eliminate black lung, operators have never suggested this.

“If eliminating CWP [coal workers’ pneumoconiosis] was that easy, there would not have been an increase in the incidence of disease in certain geographic areas since 2000. The fact that incident rates do not correlate with compliance sampling results is only a surprise to people who invest too much authority in sampling data. Exposure levels, as measured by compliance sampling, are only one part of maintaining miner health,” Bernstein adds.

“A holistic approach to protect miner health extends far beyond sampling. Over the years we have advocated for a range of additional steps to be taken – from a mandatory X-ray surveillance program for all active underground and surface coal miners to MSHA recognition and approval of non-traditional controls (such as airstream helmets) that are now available and can reduce miners’ exposure to respirable coal mine dust.”